1. Field of the Invention
The present invention relates to a non-contact communication apparatus for reading and writing information by executing radio communication in the non-contact state with an information processor and a control method for the non-contact communication apparatus.
2. Description of the Invention
At present, in place of contact IC cards, non-contact IC cards enabling non-contact communication by radio are introduced increasingly. In correspondence with it, many requests such as the reliability on non-contact IC cards, necessity of high-level print, necessity of embossing, combination with magnetic stripes, and others must be satisfied. Therefore, various non-contact IC cards are manufactured by respective systems and manufacturers.
The non-contact IC card obtains the power and a clock signal, which are necessary for the operation of itself by power supply waves sent from the reader/writer side, which is an information processor. In data communication from the reader/writer to the non-contact IC card, the power supply waves are often superimposed with data and the reception circuit of the non-contact IC card receives and demodulates the radio waves on a large level. On the other hand, the reader/writer side communicating with the non-contact IC card demodulates data from the non-contact IC card operating by the power by the power supply waves by sending the power supply waves.
As mentioned above, in the non-contact IC card, the power and a clock signal are sent and supplied from the reader/writer side, so that a supply voltage detection circuit for monitoring the supply voltage level is built in.
A conventional apparatus as mentioned above, when the supply voltage under monitoring becomes unstable, automatically stops the operation. However, when the supply voltage becomes unstable during writing and reading data from the memory, the backup becomes impossible. Therefore, a problem arises that during writing of data, the memory contents may be destroyed, while during reading of data, the data cannot be read correctly and malfunctions may be caused. When the capacity of the power supply and supply voltage detection circuit is increased so as to keep the power supply stable, it can be avoided. However, a problem arises that the circuit is enlarged in scale and cannot be mounted on one chip and even if it can be mounted on one chip, the chip area is increased and the chip is easily broken.
An object of the present invention is to provide a non-contact communication apparatus and a control method for the non-contact communication apparatus for reducing the power consumption and preventing malfunctions due to insufficient power.
According to the present invention, a non-contact communication apparatus communicating information to an external device in a non-contact state is provided. The non-contact communication apparatus comprises an antenna for receiving information transmitted from the external device or transmitting information to the external device; a control circuit connected to the antenna for controlling processes concerning a signal transmitted or received by the antenna; an execution circuit for executing a predetermined process concerning a signal transmitted or received by the antenna without operating at the same time with the control circuit; power generation means connected to the antenna for generating supply power to be supplied to each circuit of the apparatus; load generation means for generating a load when the execution circuit executes a predetermined process and applying the load to the supply power; detection means for detecting whether the supply voltage reaches a predetermined value when the load generated by the load generation means is supplied to the supply power; and a logical circuit, having power consumption lower than power consumed by the control circuit and the execution circuit, for controlling the execution circuit so as to execute a predetermined process according to an instruction of the control circuit when the detection means detects the supply voltage reaches a predetermined value.
Furthermore, according to the present invention, a control method for a non-contact communication apparatus communicating information to an external device in a non-contact state is provided. The control method comprises the steps of stopping an operation of a control circuit after the control circuit performs a predetermined control operation when processing operations relating to the writing and reading of information is to be executed; and executing a predetermined process by an execution circuit which is scheduled to operate next under control by a logical circuit with the control circuit kept stopped when the supply voltage reaches a predetermined value with the result that a load is applied to the supply power supplied from outside.